Stencil sheet and method of making an imaged stencil sheet

ABSTRACT

A STENCIL SHEET OF THE TYPE INCLUDING AN INK-IMPERVIOUS COATING OF A HEAT-FLOWABLE COMPOSITION OF THERMIPLASTIC FILM-FORMING MATERIAL COMPRISING A CELLULOSE ORGAN ESTER, AND PLASTICIZING MATERIAL PARTIALLY BUT INCOMPLETELY COMPATIBLE WITH THE FILM-FORMING MATERIAL, INCORPORATES AN ALKYLENE OXIDE ESTER OF A FATTY ACID OR AN ALKYLENE OXIDE ETHER OF FATTY ALCOHOL IN THE COATING THEREOF FOR ENHANCING STENCIL SHEET DURABILITY. PREFERABLY, A POLYMERIC HYDROCARBON RESIN ALSO IS INCLUDED FOR MIMINIZING OIL TRANSFER FROM THE STENCIL. THE STENCIL SHEET MAY BE IMAGED THERMOGRAPHICALLY, AND MECHANICALLY IN PREFERRED EMBODIMENTS.

3,824,117 STENCIL SHEET AND METHOD OF MAKING AN IMAGED STENCIL SHEET Bror E. Anderson, Arlington Heights, Margery L. Schick, Mount Prospect, and Janis E. Wedyck, Arlington Heights, 11]., assignors to Weber Marking Systems, Inc., Arlington Heights, Ill. No Drawing. Filed May 15, 1972, Ser. No. 253,394 Int. Cl. B41n N24 US. Cl. 117-355 19 Claims ABSTRACT OF THE DISCLOSURE A stencil sheet of the type including an ink-impervious coating of a heat-flowable composition of thermoplastic film-forming material comprising a cellulose organic ester, and plasticizing material partially but incompletely compatible with the film-forming material, incorporates an alkylene oxide ester of a fatty acid or an alkylene oxide ether of a fatty alcohol in the coating thereof for enhancing stencil sheet durability. Preferably, a polymeric hydrocarbon resin also is included for minimizing oil transfer from the stencil. The stencil sheet may be imaged thermographically, and mechanically in preferred embodiments.

BACKGROUND OF THE INVENTION This invention relates to a stencil sheet of the type which includes a layer of a heat-flowable composition and to a method of making an imaged stencil sheet therewith by subjecting image areas of the stencil sheet to heat generated by infrared ray absorption.

US. Pat. No. 3,694,245 granted Sept. 26, 1972, on application Ser. No. 136,373, filed Apr. 22, 1971, by the present inventors Bror E. Anderson and Margery L. Schick as a continuation-in-part of Ser. No. 674,153, filed Oct. 10, 1967, and now abandoned, discloses a thermographic stencil sheet including an ink-pervious base sheet and an ink-impervious coating thereon of a heat-flowable composition of cellulose organic ester film-forming material and plasticizing material partially but incompletely compatible with the film-forming material. The stencil sheet now is in widespread commercial use. It is employed preferably in a stencil sheet assembly including a contacting absorbent sheet on one surface thereof, and a more rigid backing sheet on the opposite surface thereof and to which which the absorbent sheet and the stencil sheet are mounted. In use, an original, such as a typed or printed sheet, is inserted between the stencil sheet and the backing sheet, and the assembly is exposed to infrared radiation on the face side of the absorbent sheet in a thermal copier such as a Weber Thermal Imager (Weber Marking Systems) or a Thermo-Fax machine (3M Company). Heat is generated in the radiation absorptive graphic portions of the original to cause the stencil sheet composition to flow in corresponding areas and thereby produce corresponding image openings in the stencil sheet. A portion of the composition rendered flowable is absorbed by the absorbent sheet and/or adjoining areas of the stencil sheet. The original and the absorbent sheet are separated from the imaged stencil sheet, the stencil sheet and the backing sheet are placed on a mimeograph duplicating machine followed by separation of the backing sheet, and the machine is operated to produce multiple mimeograph copies of the original.

It was found in use that oil was transferred from the stencil sheet to the original in the image areas. The oil frequently broadened and feathered the copy on the typed original (smudging), and the presence of oil on the original affected the imaging speed in subsequent exposures, owing to the broadening of the image characters United States Patent or transfer from the original to the stencil sheet. Subsequent performance was affected when the original was removed from the file for rerun, or in the event that optimum exposure was not used in imaging the first stencil.

It would be desirable to reduce the oil transfer to more desirable limits while preserving the advantageous properties of the stencil sheet of our aforesaid application.

In copending US. patent application Ser. No. 27,135, filed Apr. 9, 1970, by the present inventors Anderson and Schick, now US. Pat. No. 3,704,155, an improved thermographic stencil sheet exhibiting low oil transfer is claimed. The stencil sheet includes a heat-flowable composition that forms a cooled melt having a limited pourable liquid volume, and plasticizing material in the composition having limited tack and aniline point.

The improved stencil sheet claimed in the latter copending application has markedly improved oil transfer properties and in many cases also provides improved copy quality. Nevertheless, there remains room for improvement. Thus, various embodiments of the latter application do not exhibit optimum results for all of the more significant stencil performance characteristics, including imaging speed, imaging quality, oil smudging and oil transfer, blocking, and durability. Frequently, blocking occurs when oiling is reduced to a minimum. In some cases, oiling cannot be reduced to the preferred low level. At times, imaging speed or imaging quality is less than optimum.

The stencil sheet having improved oil transfer properties exhibited relatively low durability, particularly when employing the preferred formulations for the coating composition. Variations in the coating composition which were designed to increase the durability while providing low oil transfer were accompanied by sacrifices in other properties, particularly, in imaging speed, which decreased.

It would be desirable to enhance stencil sheet durability and, preferably, to further minimize oil transfer while maintaining or improving other properties, so as to approach optimum performance characteristics for a thermographic stencil sheet.

SUMMARY OF THE INVENTION The present invention provides an improvement in a stencil sheet of the type disclosed in US. Pat. 3,694,245, which enhances stencil sheet durability while maintaining or improving upon other desirable stencil sheet properties. In preferred embodiments of the invention, oil transfer is also reduced while maintaining and in many cases exceeding other prior performance characteristics.

In the invention, an alkylene oxide adduct, more particularly, an alkylene oxide ester or ether of a long chain fatty acid or alcohol is incorporated in and forms a part of the heat flowable coating composition of a stencil sheet of the type disclosed in US. Pat. No. 3,694,245. As in such prior application, the resulting composition includes a thermoplastic film-forming material comprising a cellulose organic ester, and plasticizing material partially but incompletely compatible with the film-forming material. The alkylene oxide adduct functions as a component of the plasticizing material.

In a preferred embodiment of the invention, a thermoplastic polymeric hydroca-rbon resin also is incorporated in and forms a part of the heat-flowable coating composition of the stencil sheet. The hydrocarbon resin functions in the composition both as a plasticizer for the cellulose ester and as a film-forming material, having, however, substantially lower film-forming strength than the cellulose ester. Therefore, the hydrocarbon resin is treated as a plasticizer while taking into account its film-forming properties in formulating a coating composition.

The stencil sheet of the present invention more particularly comprises an ink pervious base sheet, and an ink-impervious coating thereon of a heat-flowable composition of a cellulose organic ester film-forming material, and plasticizing material partially but incompletely compatible with the film-forming material including a member selected from the group consisting of alkylene oxide esters and ethers of long chain fatty acids and fatty alcohols, said member preferably having an HLB value (as described hereinafter) in the range of about 1.5-8. It is further preferred that the plasticizing material include a polymeric hydrocarbon resin having a total content of polymerized indenes and coumarones of at least about 30% by weight.

.The invention also provides a method of making an imaged stencil sheet, wherein the new stencil sheet is employed in contact with a graphic original, image areas of the stencil sheet are subjected to heat generated in the original by infrared ray absorption to render the composition fiowable in the stencil sheet image areas, and the composition is caused to flow from the image areas and thereby form corresponding ink-transmitting image openings in the stencil sheet. Preferred embodiments of the invention also, or alternatively, may be imaged mechanically.

A stencil sheet including an alkylene oxide adduct in the coating composition thereof according to the invention exhibits enhanced durability in using the stencil for mimeograph duplication after imaging. Inclusion of the adduct maximizes the durability obtained with various coating compositions. Thus, a stencil sheet having exceptionally high durability, as much as 50% greater than any prior sheet, may be produced when such durability is desired. Alternatively, a stencil sheet having another desirable property, for example, sensitivity to mechanical imaging, which tends to be antithetical to high durability, may be provided With a higher durability than otherwise would be obtained.

A stencil sheet also including a hydrocarbon resin may be provided according to the preferred embodiments of the present invention, that reduces oil transfer to the lowest level thus far achieved, the oil transfer being but a very small proportion of the transfer resulting from use of the preferred embodiments of Pat. No. 3,694,245. Also, the hydrocarbon resin may contribute to increase durability. At the same time, stencil quality is maintained, and imaging speed is maintained and at times increased.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The stencil sheet of the invention includes a stencil base tissue sheet that may be formed of any suitable fiber, such as abaca fiber, abaca and wood fibers, kozo fiber, or polyester fiber, loosely arranged to provide a foraminous, highly permeable tissue. The tissue may Weigh about 4 /2 to 12 pounds per 3,000 sq. ft. (24" by 36", 500 sheets), A heat-flowable coating composition, which is solid at ambient temperature, is applied to the base sheet at a rate of about 14 to 24 lbs. (dry basis), preferably about 21 lbs. per 3,000 sq. ft.

The heat-flowable coating composition preferably melts at a temperature of at least about 65 C., and it is further preferred that the coating composition melt in the range of about 65-180 C., more preferably, about 90- 160 C. (A coating composition melting point as referred to herein is determined as the temperature at which the composition on a stencil sheet visibly melts or liquefies.)

The heat-flowable coating composition includes a cellulose organic ester film-forming material, which is capable of forming a continuous, cohesive, flexible, ink-impervious film. The cellulose ester melts or is plasticizable to melt in the range of about 65-180 C. Lower alkanoic acid esters of cellulose, especially 2 to S-carbon acid esters are preferred. The preferred cellulose esters include cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate valerate, cellulose propionate butyrate, cellulose propionate valerate, cellulose butyrate valerate, cellulose propionate, cellulose butyrate, and cellulose valerate. The cellulose ester preferably is employed in a proportion in the range of about 545% by volume (652% by weight), and more Preferably about 14-30% by volume (l636% by weight) of the coating composition, including the film-forming and plasticizing materials and exclusive of additives thereto. (It has been found in practice, consistent with theoretical considerations, that volume proportions are more significant than weight proportions when substitutions of one component for another are being considered. Accordingly, the proportions of the ingredients of the coating composition for the most part are set forth herein by volume.) The preferred cellulose esters have a minimum total butyryl and valeryl content of about 35% by weight and a maximum hydroxyl content of about 4.7% by weight. The most advantageous results are obtained by employing higher total butyryl and valeryl contents, at least about 44% by weight, and lower hydroxyl contents, about 2% by weight maximum. Optimally, the total butyryl and valeryl content is at least about 48% by weight, and the hydroxyl content is below about 0.7% by weight.

Cellulose acetate butyrate is the currently preferred cellulose ester, because it both furnishes a high quality product and is readily available in the market. Of the available grades of cellulose acetate butyrate, it is preferred to employ those having a butyryl content in the range of about 35% to 55% and preferably at least about 4448%, as noted above. In the preferred grades, the average acetyl contents range from about 1.5% to 13.5%, and the hydroxyl contents range from as low as 0.1% to 4.7%, both on a weight basis. As noted above, the better products are obtained with the lower hydroxyl contents, below 2% and, preferably, below 0.7%. The preferred grades have viscosities of about 0.7-6 seconds by A.S.T.M. Method Dl34354T in Formula A, A.S.T.M. Method D-871-54T, and melting or softening points ranging from about C. to 185 0., preferably, at least about C. (determined as the temperature at which a sample first appears wet).

The cellulose ester film-forming material is combined in the coating composition with a plasticizing material partially but incompletely compatible therewith. Such plasticizing material is defined to mean material which when heated with the film-forming material in the proportions used forms a substantially homogeneous single phase melt, and which when cooled from the melt to ambient or phase of the mixture incorporating substantial proportions of both the film-forming material and the plasticizing material.

The preferred embodiments of the coating composi tion of film-forming and plasticizing materials exhibit a transition between a single-phase mixture and a twophase mixture at a temperature generally in the range of about 50180 C. Such transition temperature is referred to herein as the compatibilty temperature of the composition, and it is determined as the cloud point upon cooling the composition from a single phase melt. Thus, the first appearance of cloudiness signifies the transition from a single phase to two phases. In general, the transition is from a clear liquid to a cloudy liquid, but an obscuring material may be present without affecting performance.

Upon cooling below the compatibility temperature, the separation into two phases continues. The mixture remains fluid over a temperature range, and then the phase containing the major proportion of the film-forming material gradually hardens to a solid as the coating cools to room temperature. The remaining phase may solidify or remain liquid at room temperature. In the preferred embodiments, the remaining phase is a liquid at room temperature, forming a solid-liquid two-phase mixture thereat. The liquid phase may be trapped by the gel structure of the solid phase, or it may separate into a discrete liquid component.

As disclosed in Pat. No. 3,694,245, the plasticizing material of the coating composition may constitute a single plasticizer, or may include a variety of plasticizers. Plasticizers are substantially non-volatile substances which serve to modify the physical properties of the cellulose ester film-forming material, including the melting or softening point, compatibility, and/or cfiow properties. They may be either liquid or solid at temperatures from ambient temperature up to close to imaging temperatures, but at least must be fluid at imaging temperature in the complete plasticizing material component of the coating composition.

The plasticizers generally fall into three groups as regards compatibility with the film-forming material: Partially but incompletely compatible, incompatible, and compatible substances. Certain of the partially compatible plasticizers may be employed as sole plasticizers. Alternatively, two or more plasticizers having individual compatibilities ranging from complete compatibility to complete incompatibility may be employed, so long as the plasticizers together provide the proper balance of compatibility with the film-forming material. When a plurality of plasticizers is employed, it is highly preferable that they be compatible with each other at room temperature, forming a single phase mixture thereat, after heating together and cooling, if necessary for mixing.

The plasticizing material or complete plasticizer mix of the preferred coating composition is oleaginous or oily in nature, that is, it contains one or more oleaginous plasticizers. As disclosed in the above-identified earlier patent applications, numerous oleaginous plasticizers may be employed, such as mineral oil, castor oil, hexadecyl alcohol, polypropylene glycol monobutyl ether, polyoxethylene ethers of lanolin alcohols, pentaerythritol tetra-esters of aliphatic acids having from 5 to carbon atoms, trimethylol propane tri-esters of aliphatic acids having from 5 to 10 carbon atoms, rosin oil, polyoxethylene polyol fatty acid esters, and various other natural and synthetic oily materials. The alkylene oxide adduct employed in the present invention is oleaginous, and the hydrocarbon resin employed in the invention may be oleaginous. Numerous other plasticizers, as disclosed in our aforesaid prior applications, also may be included in the cdating composition.

A plasticizing material or complete plasticizer mix ha ving certain additional physical properties has been found to be preferable. Thus, an amorphous plasticizing material having an optimum viscosity of about 40-1 10, Saybolt seconds at 99 C. is preferred for imaging purposes. It is preferred for minimizing migration and oiliness that the viscosity of any separable liquid phase remaining in a cooled melt of the coating composition he at least about 10 centipoises at C. It is preferred for good aging properties that the plasticizing material have a maximum vapor pressure of about 0.1 mm. Hg at C. and be substantially non-hydroscopic. It is preferred for resistance to emulsion type mimeograph inks that the plasticizing material have a maximum water solubility of about 1% at 30 C.

In the present invention, it is generally most advantageous and preferred, for reasons of performance, availability and economy, to employ a mineral oil together with the alkylene oxide adduct and, when employed, the hydrocarbon resin, in the plasticizing material or plasticizer mix having the foregoing character, although others of the above-described additional oleaginous plasticizers may be employed. Mineral oil and/ or another of such oleaginous plasticizers preferably is present in a proportion in the range of about l070%,

more preferably 15-65% by volume based on the total volume of the film-forming and plasticizing materials.

The preferred mineral oils, especially petroleum oils, have a viscosity below about 10,000 Saybolt seconds (SUS) at 38 C. and, more preferably, have a viscosity above about 30 Saybolt seconds at 38 C. Mineral oils having aniline points ranging from about 15 C. (mixed aniline point) to about 115 C. (straight aniline point) have proven to be satisfactory. In general, lower aniline point oils are preferred for use with lower compatibility cellulose esters, i.e., those esters having esterifying acyl groups of lower average molecular weight, and vice versa. Aniline points are referred to herein and in the claims are determined in accordance with A.S.T.M. test D- 1012-62, except where otherwise specified. Mixed aniline point is the minimum equilibrium solution temperature of a mixture of 2 volumes of aniline, 1 volume of sample, and 1 volume of n-heptane of specified purity. Straight aniline point is the minimum equilibrium solution temperature of a mixture of 1 'volume of aniline and 1 volume of sample. Where the aniline point of a sample is too high or low for direct measurement, a material of known aniline point of opposite magnitude may be mixed withwhere A is the unknown aniline point, A is the aniline point of the mixture, A is the known aniline point, and N, and N are the volumetric fractions of the known and unknown aniline point materials, respectively. Theoretical aniline points referred to hereinafter were determined in the foregoing manner. Similarly, aniline points of plasticizer mixtures may be calculated as the average of the aniline points of the individual plasticizers, as based on their relative proportions by volume. The aniline points set forth in the examples were determined in this manner.

An alkylene oxide adduct, i.e., an alkylene oxide ester or ether of a long chain fatty acid or fatty alcohol, is included in the plasticizing material in a preferred proportion of about 5-60%, more preferably about 10-55% by volume, based on the total volume of film-forming and plasticizing materials including the adduct. Preferred adducts include ethylene oxide and propylene oxide esters and ethers of 12-20 carbon atom fatty acids and alcohols. More preferably, the adducts include 1-3.5 mols of ethylene oxide or about 30 mols of propylene oxide, reacted with a fatty acid or alcohol.

The alkylene oxide adduct is a non-ionic compound that preferably is completely soluble in or miscible with the remaining components of the plasticizing material at ambient or room temperatures, in the proportion employed. The preferred adducts have an HLB value in the range of about 1.5-8, more preferably, about 4-7. The HLB value as identified and claimed herein is an index of the hydrophile-lipophile balance as described in The Atlas HLB System, Atlas Chemical Industries, Inc. (1963). The HLB value is an indication of the weight percentage of the hydrophilic portion of a non-ionic molecule, being approximately one-fifth of such percentage, or an experimentally determined apparent value in the case of propylene oxide-containing and certain other compounds.

Preferred alkylene oxide adducts include Brij 92, Brij 72 and Brij 52 (ICI America); Volpo 3 and Provol 30 (Croda, Inc); Arosurf 66-E2 and Arosurf -E2 (Ashland Chemical Co.); Neodol 25-3 (Shell Chemical Co.); and Emery 3926D (Emery Industries).

A polymeric hydrocarbon resin preferably is includedin the plasticizing material in a preferred proportion of about 3-60%, more preferably about 1030% by volume, based on the total volume of film-forming and plasticizing materials including the resin. The preferred resins are synthetic thermoplastic resins derived from coal tar or petroleum, and more particularly, may be identified as polyindenes. They have a minimum of about 30%, preferably a minimum of 40% by weight of polymerized indenes and coumarones, including, particularly, polymers of indene, coumarone, and monoand dimethyl derivatives thereof as found in the hydrocarbon resin product mixtures. The indenes and coumarones are referred to as bicyclic monomers.

Additionally preferred hydrocarbon resins are polymers having a monomer content that is substantially limited to indenes, coumarones, and styrenes, and may also include aliphatic unsaturated monomers, particularly, cyclopentadienes. The styrenes as referred to herein, which are also termed vinyl aromatics, or monocyclic monomers, include styrene and derivatives thereof, such as the monoand dimethyl ringand side-chain substituted derivatives of styrene; ethyl styrene; divinyl benzene; and the like as found in the hydrocarbon resin mixtures. Divinyl benzene while present in some resins is not a desirable monomer, and preferably, is limited to a maximum of about 3% by Weight of the monomer content of a resin. The cyclopentadienes include, particularly, monoand dicyclopentadiene, and monoand dimethyl derivatives thereof, as also found in the hydrocarbon resin mixtures. The cyclopentadienes preferably are limited to a maximum of about 20%, more preferably, a maximum of about 10%, by weight of the monomer content of a resin.

It is further preferred that the hydrocarbon resin employed have a minimum of about 40% by weight of polymerized indenes and coumarones, and a minimum of about 80% by weight of polymerized aromatic unsaturated or aromatic olefinic monomers, including, particularly, the indenes, coumarones, and styrenes, as described above. Any remaining monomer content of the resins may substantially constitute polymerized aliphatic (including cycloaliphatic) unsaturated or olefinic monomers, particularly, the cyclopentadienes as described above. Still further, it i preferred that the monomer content of the resin include at least about 80% of polymerized indenes and coumarones, the balance being substantially (one or more) polymerized styrenes. The latter resins are identified as coumarone-indene resins, commonly produced from the crude heavy solvent naphtha fraction of coal tar light oil, and also from certain carbureted water-gas oils.

The hydrocarbon resins useful in the invention may be liquid or solid at ambient temperatures, having softening points (Ring and Ball, A.S.T.M. E-28-42T) preferably in the range of about 5-175 C. The preferred resins of greater durability are solids at ambient temperatures and have softening points above about 50 C., more preferably above about 90 C.

Useful hydrocarbon resins have a specific gravity (25 C., A.S.T.M. D-71) in the range of about 0.969-1.115, preferably about 1.016-1.145, and more preferably, about l.132-1.145. The useful hydrocarbon resins have a refractive index (n in the range of about 1.53-1.65, preferably about 1.56-1.64, and more preferably about 1.62-1.64. Useful resins in general appear to have iodine numbers (Wijs, A.S.T.M. D-1959) less than about 100, a viscosity (Brookfield) of 1 poise at about 70-270 C. and a viscosity of poises at about 40-220" C. It is preferred that the color be a maximum of about Gardner 14 (Neville 5), more preferably, Gardner 9 (Neville 2).

The preferred coal tar resins are produced by polymerization of monomers from crude heavy solvent naphthas, preferably boiling in the range of about 150- 200 C. The principal monomers present are indene, methyl indenes, coumarone, styrene, vinyl toluenes, and alpha-methyl styrene. The resins may be produced by polymerization of the monomers in the presence of a catalyst, including acid, clay and Friedel-Crafts catalysts.

Typical processes are described in US. Pats. Nos. 1,990,- 215 and 2,565,222. Preferred coal tar resins include the coumarone-indene resins identified as Cumar resins (Neville Chemical Co.), including grades R-l, R-3, R-S, R-6, LX-509', R-7, R-9, R-10, R-ll, 1 1-12, and R-l2A. Next in order of preference are Cumar resin grades R-13, R-14, R-15, R-l6, R-17, RH-17, and R-19. Additional useful Cumar resin grades include R-21, R-27, R-28, R-29, P-lO, and P-25.

The preferred petroleum hydrocarbon resins are produced by polymerization of by-product monomers obtained by high temperature, low pressure non-catalytic cracking of petroleum naphthas, natural gas, or gas-oil in the production of ethylene, propylene, butenes, butadiene, and/or isoprene. The monomers preferably boil within the range of about C. to 300 C., contain as principal polymerizable components indene, methyl indenes, styrene and vinyl toluenes, and also may contain cyclopentadiene compounds. The resins may be produced by Friedel-Crafts polymerization of the monomers, as disclosed in US. Pat. No. 3,422,052. A preferred resin produced in this manner is Neville LX-1517 (Neville Chemical Co.).

Additional useful hydrocarbon resins include Nevex 100 and Nevex (Neville Chemical Co.), Resin EC- 70 and Resin XL-30 (Velsicol Chemical Corp), and Piccoumaron 410-HL and Piccoumaron 4l0-L (Pennsylvania Industrial Chemical Corp.). The useful hydrocarbon resins are low molecular weight polymers, preferably having average molecular weights less than about 2,000, more preferably, in the range of about 290-1600, and further preferably, in the range of about 400-1200 (as determined by vapor phase osrnorneter).

One or more additional plasticizers may be included in the coating composition if desired, where adjustment of one or more stencil properties is sought. Thus, for example, other plasticizing materials are disclosed in US. Pats. Nos. 3,694,245 and 3,704,155, identified above. Also, it may be advantageous to incorporate with the coating composition a finely divided silica gel, as disclosed and claimed in application Ser. No. 30,341, filed Apr. 20, 1970, by Leonard G. Larson, Bror B. Anderson and Margery L. Schick, now US. Pat. No. 3,694,244. Applied with the composition of the present invention, the silica gel provides insurance against blocking, further minimizes oil transfer where less than optimum, and may provide an additional improvement in durability.

It appears preferable that the mixed aniline point of the complete plasticizing material or plasticizer mix in the coating composition be in the range of about 4 to 54 C. when employing cellulose acetate butyrate as the film-forming material, and more preferably, in the range of 21 to 54 C. with the preferred grades of cellulose acetate butyrate. In general, the compatibility of the cellulose ester film-former increases with the extent or proportion of acyl substitution, and the preferred aniline point of the plasticizing material increases with increased film-former compatibility, and vice versa. Thus, for example, the preferred plasticizer mixed aniline point when employing cellulose butyrate valerate is about 20 C. higher than for cellulose acetate butyrate.

The alkylene oxide adduct employed in the invention preferably has a mixed aniline point in the range of about 5 to 40 C., more preferably, 5 to 10 C. The hydrocarbon resin employed in the invention preferably has a mixed aniline point in the range of about 30' to 65 C., more preferably, 45 to 60 C. One or more other plasticizers may be blended with the adduct and the hydrocarbon resin to provide the desired aniline point for the complete plasticizing material.

The specific film-forming and plasticizing materials and proportions thereof are selected on the basis of the hereindefined properties. The film-forming and plasticizing materials are soluble in a volatile solvent and are also selected and blended in proportions so as to form a substantially homogeneous continuous imperforate coating when deposited from a solution thereof, the coating then being provided on the base sheet by deposition of the composition thereon from such solution. Preferably also, the coating is substantially clear, exclusive of the effect of additives other than the active or basic film-forming and plasticizing materials, i.e., additives such as the silica gel, pigments, fillers, and materials incorporated for other purposes. Reference to clarity also is exclusive of the opacifying effects of materials having an inherent opacity, such as waxy materials, and of the presence of materials which are solid at room temperature and are incorporated above their solubility limits at room temperature. Film-forming and plasticizing materials also are selected and blended in proportions such as to form a stencil sheet coating melting in the range of about 65180 C.

When the materials satisfy the basic or preferred conditions, the proportions of individual materials then may be adjusted within limits to achieve optimum properties.

The composition of film-forming and plasticizing materials preferably is completely soluble in a volatile solvent at a temperature of below about 60 C., more preferably, at room temperature. The preferred compositions are soluble in organic solvent mixtures of an aromatic hydrocarbon, and an aliphatic ester and/or aliphatic alcohol. The composition is deposited on the base sheet from a solution in such solvent, by evaporation of the solvent. The stencil coating formed in this manner is a uniform gel. The gel structure is changed so that the stencil coating is irreversibly physically altered when heated to the melting point of the coating, and also at times, when heated to the compatibility temperature although lower than such melting point. Accordingly, the coated stencil base sheet is dried at a temperature below the melting point and the compatibility temperature, preferably at least C. below the lower of the two temperatures.

In producing a stencil having optimum properties according to the invention, the following general sequence of evaluations may be followed:

At a selected proportion of cellulose ester, a mixture of plasticizers of diverse aniline points is combined and their relative proportions adjusted to vary the aniline point of the plasticizer mix until an aniline point optimum for the desired results is ascertained. In general, higher aniline points lead to better copy quality, slower imaging speed, more oil transfer, lower durability, better sensitivity for typing, and less blocking, and vice versa for lower aniline points. The proportion of the cellulose ester then is adjusted for optimum properties. In general, increasing the ester proportion at the same aniline point lowers the copy quality, reduces the imaging speed, decreases the oil transfer, increases the durability, reduces the sensitivity to typing, and reduces the blocking, and vice versa for decreasing ester proportions. The adjustment of the plasticizers for optimum aniline point then may be repeated with the optimum cellulose ester proportion.

An alkylene oxide adduct according to the present invention is then selected and evaluated at various proportions, employing the optimum proportion of cellulose ester and with the resulting plasticizer mix at the optimum aniline point. The aniline point and/ or the cellulose ester proportion may be adjusted once more to obtain a better balance of properties with the alkylene oxide adduct present, if necessary. In the same manner, a hydrocarbon resin according to the invention may be evaluated in the composition, together with the adduct. If desired, other plasticizers then may be substituted for the plasticizer or plasticizers employed with the adduct and the hydrocarbon resin, and/or the proportion of adduct or hydrocarbon resin may be varied with the introduction or removal of other plasticizers, for improving the product in one or more respects, or making the product more attactive commercially, more adaptable to existing equipment or available materials, and so forth. It is also found that variations in the product may be desirable for certain types of ultimate use and/or reproduction equipment.

The stencil sheet may be imaged in a conventional thermographic machine, such as a roller-type copier as represented by Weber Thermal Imager and a belt-type copier such as a Thermo-Fax Model 45CG Secretary machine. A tungsten filament lamp or other suitable source of infrared radiation is employed for imaging. A printed original in contact with the stencil sheet is exposed to radiation substantially instantaneously, i.e., on the order of about 0.03 to 0.1 second, to generate a temperature rise in the image portions of the original from about ambient temperature to a temperature sufficient to produce an imaging temperature in the image portions of the stencil sheet in the range of about 65- 180 C.

The coating composition in the stencil sheet is heated to its melting point and is reduced to a flowable condition substantially instantaneously, and a part thereof is absorbed by the absorbent sheet or into adjacent areas of the stencil sheet immediately thereafter, to leave inktransmitting image openings in the stencil sheet. The openings are bridged by the fibers of the stencil base sheet, which is ink-pervious, and the base sheet fibers serve to retain letter centers and the like in place. It is also found that a part of the coating solidifies in the image openings, after melting, and the solidified material in the openings then is in discrete particles, permitting free flow of ink around them when the stencil is employed for mimeograph duplication. After the stencil sheet is imaged, it is separated from the original and the absorbent sheet for use as a duplicating master.

In the examples which follow, the coating compositions were formulated in a solvent mixture of (in parts by weight) 50 parts of toluene, 3518 parts of ethyl acetate, 14.2 parts of ethyl alcohol denatured, US. Government Formula '0), except where another solvent mixture is indicated. T he cellulose ester was dissolved first in the solvent mixture, followed by dissolving the alkylene oxide adduct. The hydrocarbon resin and any other plasticizers, except for the mineral oil, then were dissolved. The mineral oil when employed was added last, with mixing. Where a silica gel was incorporated, it was dispersed in a portion of the solvent mixture, added to the solution of film-forming and plasticizing materials, and mixed well. In this manner, the materials of each coating composition were incorporated in the solvent mixture at a concentration of about 3035% by weight.

Stencil base tissue sheet material made of abaca fiber was coated and impregnated with a coating composition. The tissue weighed 6.7 lbs. per 3,000 sq. ft. The sheet material was coated with the composition by contacting its bottom surface with the surface of a quantity of coating composition in a dish, removing excess fluid by a doctor rod, and drying by hanging the sheets in the atmosphere at room temperature. The total coated weight of the resulting stencil sheet ranged from 26 to 30 lbs. per 3,000 sq. ft. The thickness of the resulting stencil sheet was about 2% mils.

In addition to the listed ingredients, each coating composition included 0.17 gram of dilauryl thiodipropionate antioxidant per grams of active materials.

Each stencil sheet was assembled with an absorbent sheet for thermal imaging tests, in which imaging speed and copy quality were rated. The absorbent sheet Was 10 lb. per 2,880 sq. ft. tissue formed of mixed abaca and wood pulp fibers '(Grade 55 tissue, Dexter Corporation). 'Oil smudging of the original image was determined on carbon ribbon copy typed on bond paper, and oil transfer was determined on offset printed stock. Blocking was determined by storing unassembled stencil sheets in contact with each other in foil, at room temperature. Blocking was also determined in most cases by evaluating pinholing upon exposure with a blank sheet of coated paper -1 1 in a thermal copier. Durability was determined on a Weber Model 50 (Weber Marking Systems) label printer type of mimeograph stencil duplicating machine.

(Illustrative materials which may be employed in the invention, and referred to herein are described as follows:

Cellulose Esters CAB 500-1 is cellulose acetate butyrate grade EAB 500-1 (Eastman Chemical Products) having an average butyryl content of 49.6%, an average acetyl content of 5.5%, a hydroxyl content of 01-07%, a viscosity of 018-112 seconds determined by the herelnabove-identified ASTM method, and a melting point range of about 1 65-175 C.

CAB 500-5 is cellulose acetate butyrate grade EAB 500-5 (Eastman Chemical Products) having an average butyryl content of 48%, an average acetyl content of 6%, a hydroxyl content of 0.6-1.1%, a viscosity of 4-6 seeonds (ASTM), and a melting point range of about 165- 175 C.

CAB 381-2 is cellulose acetate butyrate grade EAB 381-2 (Eastman Chemical Products) having an average butyryl content of 37%, an average acetyl content of 13.5%, an average hydroxyl content of 2%, a viscosity of 1-3.5 seconds (ASTM), and a melting point range of 171-184 C.

Half-Second Butyrate (Eastman Chemical Products) has an average butyryl content of 37%, an average acetyl content of 13.5%, an average hydroxyl content of 2%, a viscosity of 0.3-0.5 second (ASTM), and a melting point range of 155-165 C.

Tenth-Second Butyrate (Eastman Chemical Products) has an average butyryl content of 37%, an average acetyl content of 13.5%, an average hydroxyl content of 2%, a viscosity of 0.07-0.16 second (ASTM), and a melting point range of about 155-165 C.

CAB 451-1 is cellulose acetate butyrate grade EAB 451-1 (Eastman Chemical Products) having an average butyryl content of 44%, an average acetyl content of 8.5%, an average hydroxyl content of about 1.3%, a viscosity of 1-2 seconds (ASTM), and a melting point range of ISO-155 C.

CBV is cellulose butyrate valerate (Eastman Chemical Products) having an average valeryl content of about 46%, an average butyryl content of about 6%, a vis cosity of 0.9 second (ASTM), and a melting point of 120 C.

Silica Gel Syloid 255 (Davison Division, W. R. Grace Company) is silica gel having an oil absorption of about 315 lgs./ 100 lbs., a particle size range of 0.8-12 microns (90%), and an average particle size of about 3-4 microns.

Plasticizing Material Mobilsol L (Socony Mobil Oil Co.) is a refined naphthenic petroleum oil having a viscosity of '61 Saybolt Universal Seconds (SUS) at 38 C., a straight aniline point of 74 C., an API gravity of 25.7, and a distillation range of 254-370 C. (100%).

Hercolube A (Hercules, Inc.) is the mono-pentaerythritol tetra-ester of caproic acid, having an acid number of 0.1, a saponification number of 420, and a specific gravity of 1.002 at 25 C. Its mixed aniline point is 17 C.

Staybelite Ester 5 (Hercules, Inc.), is a glycerol ester of hydrogenated resin purified by steam distillation, typically having a softening point (Hercules drop method) of 81 C., an acid number of 5, a specific gravity of 1.06 at 25 C., and a mixed aniline point of 24.4 C.

Conico Paratfins (Continental Oil Co.) are normal C to C paratfins, containing 97-8% by Weight of nparaffins and 2.2% by weight maximum aromatics. The composition has a specific gravity of 0.78 at 16 C., a melting point of 8 C., a viscosity of 2.7 centistokes at 38 C., and a mixed aniline point of 82 C.

Terpex Rosin Oil (SCM Glidden-Durkee) is a terpenic hydrocarbon oil having a specific gravity of 0.945 at 155 C., a Gardner-Holdt viscosity of H-K at 25 C., and a mixed aniline point of 54 C.

BR] 559 (Schenectady Chemicals, Inc.) is an alkyd phenolic borate having a melting point of 102 C. and a theoretical mixed aniline point of C.

lHydroxy Ester of Stabilized Resin is an experimental product obtained from the United States Department of Agriculture, with a softening point of 46 C., an acid number of 9, hydroxylvalue of 31 and a theoretical mixed aniline point of 33 C.

Hydrogenated cottonseed oil (Humko Products) has a mixed aniline point of 41 C. It is a soft solid at room temperature.

Alkylene Oxide Adducts Brij 92 (ICI America) is a 2 mol ethylene oxide ether of oleyl alcohol (also referred to as a polyoxyethylene ether) having an HLB value of 4.9, an acid number of 1.0 max., and a hydroxyl number of 160-180. It has a typical viscosity of approximately 30 centipoises at 25 C. (ASTM No. D445-53T), and a theoretical mixed aniline point of -2.8 C.

Brij 72 (ICI America) is a 2 mol ethylene oxide ether of stearyl alcohol having an HLB value of 4.9, an acid number of 1.0 max., and a hydroxyl number of -170. It has a pour point (ASTM-D-97-47) of 43 C., and a mixed aniline point of 23 C.

lBrij 52 (ICI America) is a 2 mol ethylene oxide ether of cetyl alcohol having an HLB value of 5.3, an acid number of 1. 0 max. and a hydroxyl number of -180. It has a pour point of about 33 C., and a mixed aniline point of 12 C.

Volpo 3 (Croda, Inc.) is a 3 mol ethylene oxide ether of oleyl alcohol having an HLB value of 6.6, an acid value of 2 max., and a theoretical mixed aniline point of 8 C.

Provol 30 (Croda Inc.) is a 30 mol propylene oxide ether of oleyl alcohol having a mixed aniline point of 34 C.

Arosurf 66-E2 (Ashland Chemical Co.) is a 2 mol ethylene oxide ether of isostearyl alcohol having an HLB value of 4.6-5.0, a hydroxyl number of 142-152, a melting point of approximately 5 C., and a theoretical mixed aniline point of 5 C.

Arosurf 90-E2 (Ashland Chemical Co.) is a 2 mol ethylene oxide ether of oleyl alcohol having an HLB value of 5.1, and a theoretical mixed aniline point of -4 C.

Neodol 25-3 (Shell Chemical Co.) is a mixture of 3 mol ethylene oxide ethers of C C C and C linear primary alcohols, having an HLB value of 7.8, an acid value of less than 0.001, a hydroxyl number of 166, a pour point of 4 C., and a theoretical mixed aniline point of 6 C.

Emery 3926-D (Emery Industries) is a 3.5 mol ethylene oxide ester of stearic acid having an HLB value of 7 (calculated), a melting point range of 31-34 C., and a theoretical mixed aniline point of 15 C.

Hydrocarbon Resins Cumar coumarone-indene resins (Neville Chemical Co.) identified by grade designations R-l, R-3, R-5, R-6, LX-509, R-7, R-9, R-10, R-ll, R-12, R-12A, R-13, R-14, R-l5, R-16, R-17, RH-17, R-19, R-2l, R-27, R-28, R-29, P-10, an-d P-25 typically have the following monomer composition:

Range of proportions,

Monomer: percent by weight Indene 41.7-90.2 Methyl indenes 0-6.3 Coumarone 0-100 Styrene 0-14.8 Ninyl toluenes 3.2-37.0 Alpha-methyl styrene 6-6.5

13 The preferred resin grades R-l, R-3, R-S, R-6, LX-509, R-7, R-9, R-10, R-ll, R-12 and R-12A typically have the following more specific monomer composition:

,The foregoing preferred resin grades R-l through R-12A are designated collectively as Type I resins. Resin grades R-13, R-l4, R-15, R-16, R-17, RH-17, and R-l9, are designated as Type II resins. Resin grades R-2l, R-27, R-28, R-29, P-10 and P-25 are designated as Type III resins. The resins of the several types typically have the following physical properties:

Type 1 Type II Type III 1. Softening point 98-165 56-105 7-48 2-- Specific gravity, 25 C 1.132-1.145 1 Old-1.127 969-1. 099 3. Iodine number 51-65 48-76 46-84 4. Mixed aniline point, 0..... 46-56 32-62 33-64 5- Molecular weight 540-1, 150 400-800 290-530 6. Temrierague at 1 poise vis- 186-267 127-216 71-138 0081 y, 7- Temperature at 10 poises 151-220 102-171 44-98 viscosity, C. 8.- Refractive index, 25 C 1. 622-1. 634 1. 561-1. 631 1. 533-1. 611

Individual Cumar resins employed in the examples herein exhibited the following physical properties:

R-19 RH-17 R-19 LX-509 1-- Softening point, C 111.5 71. 5 56 160-165 2. Specific gravity, 25 C 1. 141 1.123 1. 016 1.134 3. Iodine number 51. 2 63. 1 53. 5 48 4. Mixed aniline point, 46. 8 42. 0 55.8

5. Molecular weight 613 445 591 1, 090-1, 148

6. Temperature at 1 poise 195 207 viscosity, C.

7 Temperature at 10 poises 159 220 viscosity, C.

8.- Refractive index, 25 C. 1. 632 1. 6241 1. 5607 1. 634

The methods of analysis for the above-numbered properties of the Cumar resins were as follows:

Neville LX-1517 (Neville Chemical Co.) is a petroleum hydrocarbon resin produced by polymerization of petroleum naphtha fractions boiling in the range of 100-300 C. and having the following typical monomer composition and physical properties:

14 MONOMER COMPOSITION Monomer Proportion percent by weight Indene 24 Methylene indenes 19 Styrene 19 Vinyl toluenes 23 Alpha-methyl styrene 3 Divinyl benzene 2-3 Other C styrenes 9-10 PHYSICAL PROPERTIES 1. Softening Point, C. 103

2. Specific Gravity, 25 C 1.062

3. Iodine Number 19-27 4. Mixed Aniline Point, C 39.9

5. Molecular Weight 840 6. Temperature at 1 poise viscosity, C 205 7. Temperature at 10 poises viscosity, C 161 8. Refractive Index, 25 C. 1.593

Nevex and (Neville Chemical Co.) are predonominantly aromatic hydrocarbon resins having the following typical physical properties:

1. Softening Point, C 102-109 2. Specific Gravity, 25 C 1.112-1.116 3. Iodine Number 54-60 4. Mixed Aniline Point, C 44.1-45.2 5. Molecular Weight 602-699 6. Temperature at 1 poise viscosity, C. 184-192 7. Temperature at 10 poises viscosity, C. 147-154 8. Refractive Index, 25 C 1.621-1.622

Piccoumaron 410-HL (Pennsylvania Industrial Chemical Corp.) is a hydrocarbon resin copolymer of primarily indene and vinyl aromatics (primarily styrene), in a weight ratio of 2.2-2.3 parts of indene per part of vinyl aromatics, having a softening point 110-115 C., a specific gravity of 1.10, a refractive index of 1.63-1.64, a theoretical mixed aniline point of 46 C., an iodine number of 36, and a viscosity (Brookfield) of 1 poise at 195- 200 C. and 10 poises at -170 C.

Resin EC-7O (Velsicol Chemical Corp.) is a hydrocarbon resin copolymer of 60% indenes, 10% coumarones and 30% styrenes (estimated proportions by weight), typically having a softening point (Ring and Ball) of 112- 118 C., a specific gravity of 1.08-1.11 (16 C.), a theoretical mixed aniline point of 48 C. and an iodine number of 80 max.

Resin XL-30 (Velsicol Chemical Corp.) is a hydrocarbon resin copolymer including indene and styrene, typically having a softening point (Ring and Ball) of 102- 107 C., a specific gravity of 1.04-1.07 (16 C.), a refractive index of 1.6, a theoretical mixed aniline point of 40 C., a saponification number of 0-2, and an acid number of 0-2.

The following examples illustrate stencil sheets having various coating compositions according to the invention. In the examples, the aniline points refer to measurements on the mixture of plasticizers, exclusive of the cellulose ester, silica gel, pigments, and solvents. The volumetric relationships are significant only for the film-forming and plasticizing materials, which constitute the herein-termed active materials, and are calculated only for such materials. It will be understood that the invention is not limited to the examples, which are merely illustrative, or to the materials, proportions, conditions and procedures set forth therein.

Example 1 Three coating compositions identified as A, B, and C were deposited on stencil base tissue, providing a total coated weight of about 26 lbs. per 3,000 sq. ft. with compositions A and B, and 27.5 lbs. per 3,000 sq. ft. with composition C. Compositions A and B varied in the grade of cellulose acetate butyrate, and compositions A and C 15 differed in that the latter included silica gel. The compositions were as follows:

All compo- Proportion, percent by srtlons, volume proportion, parts by Composition A B weight Marterial:

CAB 500-1. 16. 16. 85 19. CAB 500 16. 85 19. 9 Cumar R0 20.00 20.00 20.00 22. 4 Mobilsol L 41. 70 41. 70 41. 70 38. 1 Brij 92 21. 45 21. 45 21. 45 19. 6 Syloid 255. e 4. 0

Temperature, 0.

Mixed aniline point of plasticizer mix, 48 48 48 Compatibility temperature- 130 127-130 130 Melting point of stencil coating 116-127 128135 116-12? 6 Comp. 0 only.

Under several types of test conditions, the thermal imaging speeds of the three stencils were rated generally good, and their copy quality ratings were generally good.

Composition A had an oil smudging rating of very good and an oil transfer rating of good. Composition B had oil smudging and oil transfer ratings of good. Composition C, containing silica gel, was improved over composition A, having the ratings excellent for oil smudging and very good for oil transfer. None of the stencils exhibited blocking, for excellent ratings in this respect.

The durability of each stencil was high. The stencils from compositions A and C had desirable sensitivity for typing stencils, whereas typing sensitivity of the stencil from composition B Was low. The stencil from composition C had excellent aging properties, determined upon storage for six months at 49 C.

The Cumar R-9 hydrocarbon resin employed in this and succeeding examples, as a preferred resin, and having the composition and properties described hereinabove, was made by the PB-Sulfuric process essentially as described in US. Pat. No. 1,990,215, from feed crude heavy solvent naphtha having the following typical properties (ASTM D-850):

The following compositions A and B according to the present invention, and Composition C according to the above-identified Pat. No. 3,704,155 were compared when deposited on stencil base tissue at total coated weights of about 27-28 lbs. per 3,000 sq. ft.:

Proportion, percent by v0 ume Composition A B 0 Material:

CAB 500-1 18. 00 18. 00 18.00

Cumar 11-10. 21. 20

Mobilsol L- 38. 20 46. 30 41. 30

Brij 92 22. 60 14. 50

Staybelite Estor 21.20 21.20

Heroolube A 19. 50

Temperature, 0.

Mixed aniline point of plasticizer mix 45 48 48 The essential change in composition B from composition C was the replacement of the plasticizer Hercolube A by the plasticizer Brij 92, pursuant to the present invention. Stencil sheet durability increased by about 50% 1'6 with composition -B'. The remaining performance characteristics of the stencil sheets from compositions B and C were substantially the same.

The essential change in composition A from composition B was the replacement of the plasticizer Staybelite Ester No. 5 by the hydrocarbon resin plasticizer Cumar -R-10, pursuant to the preferred form of the present invention. The imaging speed increased from generally fair with the stencil from composition B to form good to very good with the stencil from composition A. Copy quality was good in both cases.

For compositions B and C, oil smudging was rated good and oil transfer fair. Oil smudging and oil transfer both were rated excellent employing composition A. Blocking was excellent in all cases. Durability was high for compositions A and B, and lower for C, as noted above. Typing sensitivity was similar and acceptable for all compositions.

Example 3 The following coating compositions A and B according to the present invention were deposited on stencil base tissue from a solvent composition of toluene and 20% ethanol (by weight), to provide a total coated weight of about 26 /2 to 28 /2 lbs. per 3,000 sq. ft.:

The stencil sheet from composition A had high durability. The stencil imaging speed was rated good, and the copy quality was rated good. Blocking was rated excellent. Oil smudging and oil transfer were rated fair. The stencil had high sensitivity for mechanical imaging.

The stencil sheet from composition B, containing Cumar R-9, had comparable durability to that from composition A, and also, exhibited substantially improved oil transfer properties, faster imaging, and better copy quality. The imaging speed of the stencil from composition B was rated good to very good, and the copy quality was rated very good. Oil smudging was rated very good, and oil transfer and blocking were rated excellent. The stencil sensitivity was suitable for typing.

Example 4 The following coating composition was deposited on stencil base tissue to provide a total coated weight of about 30 lbs. per 3,000 sq. ft.:

The titanium dioxide and chrome yellow pigments were included to render the image visible by contrast, which is desirable when imaging mechanically.

The stencil had very high sensitivity, suitable for imaging by data processing printers, embossed plates, typewriters at low pressure, stylus, and ball point pen. Durability was relatively low, as a concomitant of high sensitivity, but suflicient for intended use in labeling machines and hand printers.

17 Thermal imaging speed was rated good, and the copy quality was rated fair to good. Oil smudging was rated very good. Oil transfer was rated excellent. Blocking was rated excellent.

Example 5 The following coating compositions were deposited on stencil base tissue to provide a total coated weight of about 27-28 lbs. per 3,000 sq. ft:

The stencils had high durability, from fair to very good imaging speed, and from fair to good copy quality. Oil smudging was rated from good to excellent, and oil transfer and blocking were rated excellent for all stencils.

Example 6 The following coating compositions when deposited on stencil base tissue to provide a total coated weight of 27 /2 to 30 lbs. per 3,000 sq. ft. resulted in improved stencil sheets according to the invention:

Proportion, percent by volume Composition A B C D E Material:

GAB 500-1 15.70 15.70 30. 00 16.85 16.30 Cumar R-9 Mobilsol L-..

Brij Q2 BRJ' 559 Hydroxy ester of stabilized res Hydrogenated cottonseed oi1 Temperature, C.

Mixed aniline point of plasticizer mix 48 Except for composition C, having very high durability with low sensitivity, the stencil sheets are suitable for imaging by typewriter as well as thermographically.

Example 7 The following coating compositions when deposited on stencil base tissue to provide a total coated weight of 26 /2 to 28 /2 lbs. per 3,000 sq. ft. resulted in improved stencil sheets according to the invention:

Proportion, percent by volume 13 1 C D E F Composition A 1 Material:

Tenth-second Resin XII-30.

Mobilsol L 18. 30 18.20 30. 20 34. 50 4 00 43. 30 Brij 92 43.70 43.80 31.80 47. 50 19.40 28.15 18.70

Temperature, C.

Mixed aniline point of plastieizer mix Example 8 The following coating compositions when deposited on stencil base tissue to provide a total coated weight of 26 /2 to 28 /2 lbs. per 3,000 sq. ft. resulted in improved stencil sheets according to the invention, suitable for imaging both thermographically and by typewriter:

Proportion, percent by volume Composition A B C D E F G Material:

CAB 500-1 16.85 18.00 15. 70 16. 85 16.85 18. 00 18.00 Cumar LX509- 20. 00 Nevex 100... 20.00 Piccoumaron Temperature, 0. Mixed aniline point of plasticizer mix 48 48 38 31 37 31 Compatibility temperature 127 Example 9 The following coating compositions when deposited on stencil base tissue to provide a total coated weight of 26 to 28 /2 lbs. per 3,000 sq. ft. resulted in improved stencil sheets according to the invention:

Proportion, percent by volume Composition A B O D Material:

CAB 500-1 Cumar R-9. Mobilsol L Conoco paraflins 'Ierpex rosin 011 Temperature, C.

Mixed aniline point of plasticizer rm'x 48 48 48 48 Compatibility temperature 93 We claim: 1. In a stencil sheet including an ink-pervious base sheet, and an ink-impervious coating thereon of a heatflowable composition of thermoplastic film-forming material comprising a cellulose organic ester, and plasticizing material partially but incompletely compatible with said film-forming material, the improvement which comprises a member selected from the group consisting of alkylene oxide esters and ethers of long chain fatty acids and fatty alcohols included in said plasticizing material in a proportion of about 5-65% by volume based on the total volume of the film-forming and plasticizing materials, said member having an HLB value in the range of about 1.5-8.

2. A stencil sheet as defined in claim 1 wherein said alkylene oxide is ethylene oxide.

3. A stencil sheet as defined in claim 1 wherein said alkylene oxide is propylene oxide.

4. A stencil sheet as defined in claim 1 wherein said member is a 13.5 mol ethylene oxide ether of a 12-20 carbon atom fatty alcohol.

5. A stencil sheet as defined in claim 1 wherein said member is a 30 mol propylene oxide ether of a 12-20 carbon atom fatty alcohol.

6. A stencil sheet as defined in claim 1 wherein said cellulose ester is selected from the group consisting of 19 cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate valerate, cellulose propionate butyrate, cellulose propionate valerate, cellulose butyrate valerate, cellulose propionate, cellulose butyrate, and cellulose valerate.

7. A stencil sheet as defined in claim 1 wherein said plasticizing material also includes a mineral oil.

8. A stencil sheet as defined in claim 1 wherein said plasticizing material also includes a thermoplastic polymeric hydrocarbon resin in a proportion of about 3-60% by volume based on the total volume of the film-forming and plasticizing materials, said resin having a total content of polymerized indenes and coumarones of at least about 30% by weight.

9. A stencil sheet as defined in claim 8 wherein said resin is a coal-tar coumarone-indene resin having a total content of polymerized indenes and coumarones of at least about 80% by weight and the balance substantially polymerized styrenes.

10. A stencil sheet as defined in claim 8 wherein the softening point of said resin is above about 90 C.

11. In a stencil sheet including an ink-pervious base sheet, and an ink-impervious coating thereon of a heatflowable composition of thermoplastic film-forming material comprising a cellulose organic ester, and plasticizing material partially but incompletely compatible with said film-forming material and including a mineral oil, the improvement which comprises,

a member selected from the group consisting of alkylene oxide esters and ethers of long chain fatty acids and fatty alcohols included in said plasticizing material, said member having an HLB value in the range of about 1.5-8, and

a thermoplastic polymeric hydrocarbon resin included in said plasticizing material, said resin having a total content of polymerized indenes and coumarones of at least about 30% by weight,

the proportions of said materials being about -45% of said ester, about 5-65% of said member, about 360% of said resin, and about 10-70% of said mineral oil, in proportions by volume based on the total volume of the film-forming and plasticizing materials.

12. A stencil sheet as defined in claim 11 wherein said cellulose ester is cellulose acetate butyrate.

13. In a stencil sheet including an ink-pervious base sheet, and an ink-impervious coating thereon of a heatfiowable composition of thermoplastic film-forming material comprising a cellulose ester selected from the group consisting of cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate valerate, cellulose propionate butyrate, cellulose propionate valerate, cellulose butyrate valerate, cellulose propionate, cellulose butyrate, and cellulose valerate, and

plasticizing material partially but incompletely compatible with said film-forming material, the improvement which comprises including in said plasticizing material (a) a member selected from the group consisting of alkylene oxide esters and ethers of long chain fatty acids and fatty alcohols, said member having an HLB value in the range of about 1.5-8, and

(b) a thermoplastic polymeric hydrocarbon resin having a total content of polymerized indenes and coumarones of at least about 30% by weight,

the proportions of said materials being about 5-45% of said ester, about 5-65% of said member, and about 33-60% of said resin, in proportions by volume based on the total volume of the film-forming and plasticizing materials,

said heat flowable composition forming a substantially homogeneous single phase melt, and when cooled from the melt having a cloud point in the range of about 50-l80 C., and forming a two-phase mixture at room temperature, at least one phase of said mixture incorporating substantially proportions of both said film-forming material and said plasticizing material,

said heat flowable composition being soluble in a volatile solvent and forming a substantially homogeneous continuous imperforate coating when deposited from a solution thereof, and said coating being provided on said base sheet by deposition of said composition thereon from a solvent solution of the composition and removal of solvent therefrom, the melting point of said coating being in the range of about 65180 C., said coating further becoming flowable and irreversibly physically altered when heated to its melting point for forming ink-permeable image areas in the cooled stencil sheet.

14. A stencil sheet as defined in claim 13 wherein said cellulose ester has a minimum total butyryl and valeryl content of about 35% by weight, and a maximum hydroxyl content of about 4.7% by weight.

15. A stencil sheet as defined in claim 14 wherein the monomer content of said resin is substantially limited to indenes, coumarones, styrenes, and aliphatic unsaturated monomers, and said resin has a total content of polymerized indenes and coumarones of at least about 40% by weight, and a total content of polymerized indenes, coumarones, and styrenes of at least about by weight.

16. A stencil sheet as defined in claim 13 wherein said plasticizing material also includes a mineral oil in a proportion of about 1070% by volume based on the total volume of the film-forming and plasticizing materials.

17. A stencil sheet as defined in claim 13 wherein the softening point of said resin is in the range of about 5- 175 C.

18. In a stencil sheet including an ink-pervious base sheet, and an ink-impervious coating thereon of a heatfiowable composition of thermoplastic film-forming material comprising cellulose acetate butyrate having a minimum butyryl content of about 35% by weight and a maximum hydroxyl content of about 4.7% by weight, and plasticizing material partially but incompletely compatible with said film-forming material and including a mineral oil, the improvement which comprises including in said plasticizing material (a) a 1-3.5 mol ethylene oxide ether of a 12-20 carbon atom fatty alcohol, said ether having an HLB value in the range of about 1.5-8, and (b) a themoplastic coal-tar coumarone-indene resin having a total content of polymerized indenes and coumarones of at least about 80% by weight and the balance substantially polymerized styrenes, and a softening point in the range of about -175 C., the proportions of said materials being about 5-45% of said cellulose acetate butyrate, about 5-65% of said ether, about 3-60% of said resin, and about 10-70% of said mineral oil, in proportions by volume based on the total volume of the film-forming and plasticizing materials, said heat flowable composition forming a substantially homogeneous single phase melt, and when cooled from the melt having a cloud point in the range of about 50-180 C., and forming a two-phase mixture at room temperature, at least one phase of said mixture incorporating substantial proportions of both said film-forming material and said plasticizing material, said heat flowable composition being soluble in a volatile solvent and forming a substantially homogeneous continuous imperforate coating when deposited from a solution thereof, and said coating being provided on said base sheet by deposition of said composition thereon from a solvent solution of the composition References Cited and removal of solvent therefrom, the melting point UNITED STATES PATENTS of said coating being in the range of about 65-180 C., said coating further becoming fiowable and ir- 3,368,989 2/1968 Wlssmger et a1 117 36-1 reversibly physically altered when heated to its melt- 3,052,675 11/1962 Shelfio 117-355 ing point for forming inkmmeable image areas in 5 3,704,155 11/1972 Anderson et al 117-355 the cooled stencil sheet. 3,120,611 2/1964 Lmd 117-361 19. A stencil sheet as defined in claim 18 containing, in 3,250,637 5/1966 Frasher et 117-355 proportions by volume based on the total volume of the 3,177,086 4/1965 Newman 61 117-361 film-forming and plasticizing materials, about 14-30% of 3,446,662 5/1969 Newman a] said cellulose acetate butyrate, about 10-55% of said ether, 10 about 10-30% of said resin, and about 15-65% of said WILLIAM MARTIN Pmnary Examm" mineral oil, said cellulose acetate butyrate having a mini- W, R, TRENOR, Assistant Examiner mum butyryl content of about 44% by weight and a maximum hydroxyl content of about 2% by weight, and 15 US. Cl. X,R,

sta d ether having an HLB value in the range of about 106 189, 191; 117 36 1 1&7; 250 65 T mmrr STATES PATENT @FFICE QETEFEATE @F @QRREUHQ Patent No. 3 ,824 117 Dated July 16, 1974 fllnventoi-(s) Bror E. Anderson, Margery L. Schick, 8a Janis E. Wedyck It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

601mm 1, line 4J2: Emilee which, seesaw ecmzrreme;

3, M Change increase is -imcrewed- 4, 5%.. After "or" insert remm temperature form a two-passe mixture, at least ome--;

11, m: Change ""Gwnicm" rm --Cemwsw--;

1% 3'7: After "seftenimg point" insert --of--;

m, 22: Change the numeral "33"to -3l- Signed and sealed this 18th day of February 19'75.

(SEAL) Attest CZa MARSHALL DANN RUTH C. MASON Commissioner of Patents Arresting Officer and Trademarks FORM PO-IOSO (10-69) USCOMM-DC 60375*P59 i U.S. GQVERNMENT PRINTING OFFICE: I969 0-356-334. 

